Posted
by
Soulskill
on Friday March 23, 2012 @09:57AM
from the don't-let-ian-mckellan-get-his-hands-on-this dept.

ananyo writes "Researchers have made a cloak that can hide objects from static magnetic fields, realizing a theoretical prediction they made last year. This 'antimagnet' could have medical applications, but could also be used to subvert airport security. The cloak's interior is lined with turns of tape made from a high-temperature superconductor. Superconductors repel magnetic fields, so any magnetic field enclosed within a superconductor would be undetectable from outside. But the superconductor itself would still perturb an external magnetic field, so the researchers coated its external side with an ordinary ferromagnet. The superconductor tries to repel external field lines, whereas the ferromagnet tries to draw them in — together, the two layers cancel each other out (abstract)."

Do they make liquid nitrogen storage dewars of less than three ounces?

If so, I don't think that there is anything about cryogens(so long as they aren't compressed, compressed gas cylinders not Specifically Approved have been on the list for at least a decade before the security theatre opened in earnest).

If that dewar contains more than three ounces of liquid, though, you'd better touch your toes and think of Freedom while I get the exam glove.

I would not take a dewar of any cryogenic liquid onto an aircraft - I don't even ride in the lift with them. That said, a small volume wouldn't pose all that much of an asphyxiation hazard. I carry LN2 around in a cheap thermos bought at the grocery store and you can keep it liquid that way for hours.

"If that dewar contains more than three ounces of liquid, though, you'd better touch your toes and think of Freedom while I get the exam glove."Why would I be touching my toes while you are getting rectally probed? Is this like a wrestling tag team match?

What, poor people can't get in through the rich lines? Well, a Fortune 500 CEO flying on a private jet surely has assistants, security, and other personnel, and he'll be damned if some "airport security" will hold up his tee time in Cabo!

I wonder how long it will take for someone to exploit this particular attack vector.

Anybody who has their own plane pretty much does whatever they want. I've landed my plane at large airports (EG: Oakland, CA) with extensive security lines for commercial flights, and driven my car out to the plane in order to load it. The only credentials I need are the keys to a plane and maybe a driver's license.

I've landed my private plane at big airports in order to hook up with commercial flights, and it's truly absurd to land, walk in off the tarmac, be personally greeted at the private aviation side of the airport, and then take a shuttle to be treated like a potential criminal in a cattle stock yard. This affords me very little respect for the TSA.

You don't need to be a Fortune 500 CEO to have a private plane, the actual cost to own (especially for a time share aka "flight club") can be similar in cost to owning a recent model car.

Alternatively, they may just put all of the related researchers under surveillance, which seems like the more natural thing to do for them. The physicists aren't their friends, after all; they're just ordinary citizens.

Sorry, but you're thinking with a level head here--that's now how these decisions get made. DHS does not exist to solve a problem via positive improvements. It exists to solve a problem via control, invasive action, and denial of freedom. That's much easier to do than to be inclusive, pro-active, and innovative. Unfortunately, it's also not nearly as effective, either. In the long run, it's a losing battle. DHS/TSA function the same way as the RIAA/MPAA - fighting the battle in the wrong way, wasting

You could likely cool your high temperature superconductor to nearly absolute zero (thus over a hundred kelvin of leeway), then encase it in aerogel or some similarly powerful insulator (vacuum?). This setup should last long enough for mobile applications of this technology.

Of course, if you have the resources and knowledge to implement this, just build a death ray and shoot down the plane. I don't have any idea why people keep thinking of ridiculous ways around TSA agents and security theater checkpoi

You only need half of the equation (the superconductor) to do that. You don't care about "cloaking" anything when trying to dissipate the MRI field, you just get rid of it.

As far as I know (and admittedly, when it comes to MRI machines that isn't a great deal) there isn't any real technical hurdle regarding removing it's magnetic field. It would be annoying (keeping even a high temperature super conductor cool), expensive, and a lot harder than just telling everyone to empty their pockets.

What you are talking about are called gradients in MRI. There is also an RF magnetic field used for MR excitation. The gradients and the RF are not the reason you have to empty your pockets, it is the static field, which is orders of magnitude larger, and has the potential to dangerously accelerate metal objects towards the magent. In the absense of the static field, it would be no problem for bystanders / people around the magnet to have metal.
Patients should make known any metal they have on their body,

Since metal detectors use electromagnetic waves (call those non-static magnetic fields if you want), instead of magnetic fields, that cloak wouldn't be a problem at all. Well, ok, it would cloak its interior, like any piece of conductor would. It would also trigger the alarm itself, like any piece of conductor.

But now, why are people so concerned about airport security anyway? The invention has no relation to it.

We aren't - but since some **** put it in the summary (may be the submitter, probably an editor), it makes it fair game to talk about. I'm sure we all cringed when reading the summary and had a bunch of pointed disparagements towards the submitter / editor run through our heads. I know I did.

The reason I ask is that some have been misled to believe that aluminum foil works just as well. But those of us who use actual tin foil hats know that aluminum foil doesn't work.

"They" can penetrate aluminum foil with their mind control rays so "they" worked to drive down the price of aluminum foil while making real tin foil more expensive. This was done in conjunction with a "grass roots" whisper campaign selling the virtues of aluminum foil as blocking their mind c

Because it's not "high temperature" in any sense that would be understood by the term.

It's called high temperature because it's significantly hotter than temperatures where superconductivity occurs in ordinary metals (around 30K). But even the highest temperature at which superconductivity has ever been observed is still freakin' cold... over a hundred degrees below 0

Until room temperature superconductivity is discovered (an enormous breakthrough in physics that would have countless applications), nothing's getting by airport security with this mechanism.

That was my first thought. But this might end up being a good prod to get true high temperature superconductor research a super boost. One of the main methods used to detect submarines in the military are magnetic anomaly detectors usually attached to a plane or helicopter. The aircraft don't even need to dip them in the water, just fly over and look for magnetic anomalies (granted the sub needs to be fairly close... but I'm not sure if the military tells anyone what counts as really close). So the crux is that if this will help hide their subs, DARPA and the military might be inclined to shovel piles of money into high temperature superconductors. Although I'm sure they have financed this in the past, this direct applications of stealth for submarines could help with an improved cash flow (or maybe this project is financed this way already.... ?). mmmmm blah blah blah... profit! Or something like that.

Don't worry, the military is already lots interested in superconductors that work at room temperature.

More money would help, more money is more eyes on the problem. But frankly the superconductor field is kind of waiting for it's Einstein if you will. We fundamentally lack understanding about some key things and more than likely it's only going to be solved when somebody has the eureka moment.

Or people who don't actually understand that the term is relative to the normal temperature levels of superconductivity, and not relative to what a person without any knowledge of it would normally think when they hear the words "high temperature".

Honestly, I don't doubt that this will turn out to have 'security' uses, it just seems like dicking around with aircraft isn't going to be one of them...

Magnetometers of substantial sophistication have been in use since at least WWII for naval detection and fuzing applications. Surely somebody is already writing up the proposal for a submarine and/or torpedo with a superconductor layer that can be cooled on demand to provide full magnetic field stealth...

I was about to mention mumetal, but its claim to fame is very high permeability. It doesn't repel magnetic fields, it Shamwows them. I suppose if the mumetal is saturated from the inside, then it doesn't hide the object from an external field. Although it takes a lot to saturate properly treated mumetal.

Old man story time. My Tektronix 547 CRT oscilloscope has its CRT encased in a mumetal shield. I got a powerful magnet and put it on the side of the case, the trace didn't budge at all. Great stuff. Of course, mumetal loses its properites if it's dinged, deformed or otherwise mechanically abused.

Currently, high temperature superconductors work up to around 100K- which is about -170C. So currently you would need a liquid nitrogen cylinder to contain the cloak and keep it cold enough. Then you would need to hide that in some other way. somehow I don't think that is likely.
Room temperature superconductors are some way off- they know how low temperature (few kelvin) superconductors work, but are not sure how the high temperature conductors work- so researchers are not sure how to improve on the curre

Terrorist Jim: Bob, we will have you wear the antimagnet cloaking suit. All we have to do is have you walk into a restroom right before you go through the scanner, open this forty gallon Thermos container and pour the liquid nitrogen all over yourself.

You'll walk to airport security and pass through the security check with no problems.

Day of the terrorist strike.

Bob enters the airport dragging a heavy carry-on suitcase. His suit is disproportionately large compared to his body, and seems quite stiff. He

A friend and I were discussing the ramifications of superconducting racetracks [youtube.com] for low-friction transportation. One of the problems he brought up was how to deal with intersections. Quantum levitation locks your maglev car into a certain orientation relative to a magnetic field. But at an intersection the magnetic field changes. Either you stop levitating, or your car comes to a screeching halt as if it had hit a brick wall.

Something which can shield from static magnetic fields would allow two magnet